Discussion Paper on Baseline

Draft, Nov. 2, 2005

Background

Since the release of the WCAG 1.0 in 1999, the World Wide Web has evolved
considerably. The WCAG 1.0 was written assuming that Web users would
primarily be using HTML. Today, the Web is used in hundreds ways that were
not possible in 1999. Many new Web technologies are emerging and existing
technologies are becoming more comprehensive as the Web community finds new
and original ways to disseminate information and interact with it. Also, due
to language, economic differences and other factors, technologies that are
common in one part of the world may not be present, or may not be as up to
date, in others.

Given these realities, the WCAG working group realized that it would have
to find a different basis upon which to form version 2.0 of the guidelines.
It would have to present Web accessibility as a set of principles that would
work across all of today's technologies and that would be robust enough to
withstand dramatic shifts and changes in technology. The WCAG 2.0 would have
to apply to a wide range of W3C and non-W3C technologies. It would need to be
a document that would give policy makers and managers guidance about what
outcomes are necessary when striving to create accessible Web content, yet
allow for differences between technologies and cultures without introducing
guidelines that are incompatible between countries.

To address these needs the working group has developed a set of guidelines
(with success criteria) that are technology independent. This guideline
document is accompanied by a second information document (called
Understanding WCAG 2.0) that provides examples and lists of techniques that
are sufficient to meet the guidelines. This two-layered approach makes it
possible to have stable criteria for accessibility with supporting technical
documents that will be "evergreen" and updated as the technologies evolve.

A key element in this model is the ability to define the set of
technologies that user agents can be assumed to support. The group, however,
found that any set of technologies it chose would quickly date the guidelines
as the last guidelines were. It would limit the ability of Web content that
is accessible in the future, using future technologies, to claim conformance
using those new technologies. After trying to solve the problem several times
in this manner (including trying out UAAG to define the set of technologies,
see below), the working group determined that the only way to solve the
problem was to introduce a new concept: "baseline".

What is a baseline?

A "baseline" (as used in WCAG 2.0) is a set of technologies that a user
agent (browser, media player, screen reader etc.) is assumed to support and
have enabled. The Baseline may be set by the author or someone above them.
When an author makes a WCAG 2.0 conformance claim, they must specify the
Baseline that they are using to make that claim. The author is claiming that
their content will meet WCAG 2.0 at the stated level of conformance if a
user's agent can support those (the baseline) technologies.

The author may actually rely on only some of the technologies in the
baseline (a subset of them). When they make their claim they can therefore
also say exactly what they are relying on for their claim. This is a more
precise description of the part of the baseline that they are relying on and
can be helpful to consumers whose user agent does not fully support the named
baseline. (This additional "relies on" information would be optional in a
conformance claim).

Developers may choose to use additional technologies that are not in the
minimum set (the baseline) provided that the following are true:

The Web content is still operable using user agents that only support
the technologies that are in the minimum set (i.e. the use of
technologies that are not in the minimum set does not "break" the Web
content for user agents that don't support them.)

All information and function must be available using only the baseline
technologies.

Examples of Baselines (and what they mean) include

Example 1 - Baseline is: HTML 4.01 Transitional

If the user agent supports this technology, then the content meets WCAG
2.0 at the level the author claims.

This content might also use CSS2, Real Video, Real Audio, and MP3.
However, even if the user's agent does not support these, the content claimed
would still meet WCAG 2.0 at the level claimed.

Example 2 - Baseline is: XHTML 1.0 (Strict), CSS2, JavaScript 1.2

If the user agent supports these technologies, then the content meets
WCAG 2.0 at the level the author claims.

This content might also use other technologies. However, even if the
user's agent does not support these, the content claimed would still meet
WCAG 2.0 at the level claimed.

The Baseline #1-2006 might include for example HMTL 4.01, gif, jpg, avi,
mov, and a few other commonly supported technologies.

If the user agent supports the technologies in that baseline, then the
content meets WCAG 2.0 at the level the author claims.

The author may only use a subset of these technologies in the web pages
they are claiming. They may therefore state that they are only relying on
HTML 4.01 and gif. That would mean that their pages would conform to WCAG 2.0
at the claimed level if the users' user agents only supported these
technologies. Note that the "relies on" technologies must always be a subset
of the Baseline technologies.

This content might also use JavaScript 1.2, CSS2, PDF and Flash. However,
even if the user agent does not support these, the content claimed would
still meet WCAG 2.0 at the level claimed.

Baseline specifications are not browser specifications

The baseline is not the same as statements such as "this Web content works
best using IE 6.0". This would be an invalid baseline statement. The baseline
is not browser-specific nor user agent specific. It is a set of technologies.
There is a subtle but important distinction. One reason it is important to be
technology-specific rather than user agent specific is that restricting users
to specific user agents may pose insurmountable accessibility problems for
some people. It would be almost impossible to know all of these problems in
advance unless perhaps the content was to be used in a closed environment.

Baselines are not about audience abilities

The baseline statement is a not a statement about what physical, sensory
or cognitive abilities are required to use content. It is a
technology-specific statement about what technologies a user agent needs to
support for the content to be accessible at the claimed level.

One assumption that must be made by all stakeholders who are creating Web
content is that the target audience will include people with disabilities.
People with disabilities are to be considered an integral part of all
demographics. As a part of a conformance claim one cannot exclude people with
disabilities from the target audience.

Using baselines in conformance claims

In claiming conformance to WCAG 2.0, developers are claiming that all
information and functionality of the Web content conforms to WCAG 2.0 at a
given level if the user agent supports the stated baseline technologies.

Over time, the baselines used by various organizations and governments may
change to accommodate new technological advances. The intention of the WCAG
2.0 is that the principles and functional outcomes of the guidelines remain
stable during technological change because they are both technology
independent and baseline independent.

Who sets the baseline?

Although there was no mention of a baseline in the 1999 WCAG 1.0
Guidelines, there was an implicit baseline used for those guidelines. Simply
put, the WCAG 1.0 assumed a baseline of HTML, and a few graphic and media
technologies. In this respect, a baseline was assumed and was "hard wired"
into the specifications. Since WCAG 1.0 was written with HTML in mind, a
baseline was set by and included in the guidelines themselves. The
constraints this presented were a key reason for the need for WCAG 2.0.

In the WCAG 2.0 Guidelines, no particular baseline is assumed. Instead the
baseline is assumed to be set outside of the WCAG 2.0 document. The baseline
may be set by any one of a number of sources.

Government or corporate policy may decide what technologies are in the
baseline.

It could be set by a customer that would require certain technologies
and features.

It could be the author's company that sets a baseline for them to
use.

If no one else above the developer sets the baseline, then the
developer would set it.

The WAI may
provide guidance in setting baselines, but is not setting "The Baseline" or
"A Baseline" for WCAG 2.0.

If the WCAG does not set the baseline, then how can we be sure that a
site will be accessible?

No site or content is ever completely accessible.

Conformance to WCAG 2.0 at some level provides that level of accessibility
for users whose agents can support the stated baseline technologies for that
content.

If developers chose a baseline that is too high, that includes too many
technologies that are not supported by user agents in use by people with
disabilities, then those sites or that content may not be accessible to those
people. It is up to developers to use baselines that are reasonable and
appropriate to the times and the technical levels of user agents of people
with disabilities.

If developers do not use reasonable baselines, then it is up to companies,
customers or regulatory agencies to set baselines that are appropriate for
the time.

What is available to help developers choose a baseline?

There will be an "How to meet SC x.x.x" document for each success
criterion. This "how to meet" document will include key terms, the intent,
sufficient and optional techniques, common failures, who benefits, examples,
and related resources for further information for that WCAG 2.0 success
criterion. Within some of these documents (where appropriate) there will be
example baselines for various circumstances. These can be used as templates
that can be adapted to specific environments.

The W3C-WAI may also prepare "A Guide for Policy Makers" to help
organizations choose a baseline that will ensure the maximum accessibility
for their environments. There may also be resources that describe what user
agent support is available in different languages and different
geographies.

What other aids will be available for developers?

W3C technologies

The WCAG will provide technology-specific techniques documents for various
W3C technologies. Where the "How to meet..." documents describe sufficient
ways to meet each success criterion of the guidelines, the technique
documents will provide detail on both sufficient and advisory techniques
including examples, code, and test procedures where appropriate.

Non-W3C technologies

W3C is not in a position to create guidance documents for other companies'
technologies. However W3C is working with them to develop similar
materials.

Most major non-W3C technology providers are in the process of developing
accessibility techniques that will help users of their technologies meet the
WCAG guidelines. Just as with W3C technologies, in order to claim
conformance, any content using these technologies will have to meet all of
the level 1 WCAG 2.0 success criteria.

For non-W3C technologies that do not have their own techniques documents,
the functional outcomes described in the success criterion can be used to
evaluate content for accessibility at the three WCAG 2.0 levels of
conformance.

Why wasn't UAAG used as Baseline?

The User Agent Accessibility Guidelines (UAAG) will provide helpful
direction to stakeholders who are choosing a baseline. It was a serious
consideration of the working group to use the UAAG as the WCAG 2.0 baseline.
In fact, the working group tried to do that at one point. However, after
careful consideration and much effort and research, it was determined that
the UAAG would not be a workable baseline for the WCAG for many reasons
including the following:

The Baseline is about technologies — not user agents. So UAAG must be
transformed from user agent specifications to technologies used by user
agents. This was complicated but not insurmountable.

Many of the UAAG specifications don't actually require support for
technologies or capabilities in the User Agent; they just provide
specifications for what should be true if they are supported. Thus, much
apparent guidance was optional.

Today, there are no user agents that fully conform to UAAG (support
all the technologies in the way specified in UAAG).

The WCAG would have to recommend repair techniques that compensate for
User Agents that don't conform to UAAG, which could create confusion
about what conformance means.

UAAG doesn't answer key questions about how Assistive Technology
capabilities interact with user agent capabilities — yet AT is an
essential part of the user agent for many people with disabilities.

There are financial and language considerations, that are outside the
scope of the UAAG. Many capabilities assumed by UAAG do not exist in many
languages.

Using the UAAG as the baseline could mean a baseline that would only be
met by the most popularly supported Assistive Technologies which are only
available in some languages.

In Closing

The technological environment of today is vastly different from that of
1999 when the WCAG 1.0 was released. We need to respond to these new
realities in a way that will empower people with disabilities in this new
environment while facilitating effective technological innovation,
communication, and commerce on the Web. The baseline concept is a proposed
response to these challenges. It also reflects our experience of watching the
implementation of the WCAG 1.0 over the past number of years. We seek
comments and suggestions and welcome your input.

The Baseline used to make the conformance claim. (If baseline is a
published baseline it can be named along with a URI that points to it.
The baseline technologies can also be spelled out individually in the
conformance claim. )

Scope of the claim (a URI, list of URI's or a regular expression).

Optional components of a conformance Claim

A list of the specific technologies "relied upon" to create the content
for which the claim is being made.

Example 2

On 1 August 2006, "S5: An Introduction"
http://meyerweb.com/eric/tools/s5/s5-intro.html conforms to W3C's WCAG 2.0.
Conformance Level 1. The baseline for this claim is UDBaseline#1-2006 at
http://UDLabs.org/Baseline#1-2006.html. The specification that this content
relies upon is: XHTML 1.0 (Strict). The specifications that this
content uses are: JavaScript 1.2, CSS2, png, and jpg.

Vertical and Horizontal Scoping in Conformance Statements

Question

We are planning to have our content conform to the WCAG 2.0 except for a
section where people post information and files. We cannot always be sure
they will post conforming content. What do we do?

Answer

Authors cannot claim conformance for any section of web content that
cannot be guaranteed to conform to the guidelines. One common place this
might occur is public forums where organizations may not have complete
control over what is posted to their content.

To handle this and similar situations WCAG 2.0 includes the concept of
scoping. A conformance claim may "scope out" specific sections of a site.
This is "vertical scoping" (scoping out a portion of a site by URI or URI
range) and is allowed. WCAG 2.0 conformance can be claimed for any portions
of a site and/or can claim all but certain sections of the site.

"Horizontal scoping" (scoping out a particular technology within delivery
units) is not allowed. A company could not say something like "our content
conforms to the WCAG 2.0 at level 1 except all the navigation menus are not
compliant," or, "our content conforms except for all the multimedia and
animations." This would be scoping out parts of various delivery units and
would not be a valid or acceptable WCAG 2.0 conformance claim. Any Web
content (delivery unit or set of delivery units) that is part of a
conformance claim must meet all of the Success Criterion for the level that
it claims.

Examples of People and Places Setting Baselines

Example 1: A government site that provides information to the
public
A government agency publishes information intended for the general
public. The specified baseline includes only technologies that have been
widely supported by more than one accessible and affordable user agent for more than one release.

Example 2: A government adopts a guideline for use with
accessible user agents in use by its citizens
A government periodically changes the baseline it requires for developers
of public sites to reflect the increasing ability of affordable user
agents (including assistive technology) to work with newer
technologies.

Example 3: A government provides accessible user agents to all
citizens
A government provides all citizens with user agents that support newer
technologies. The government specifies a baseline that includes newer
technologies that are supported in the user agents provided by that
government.

Example 4: A private intranet
A company or government agency provides its employees with the
information technology tools they need to do their jobs. The baseline for
intranet sites used only by employees includes newer technologies that
are supported only in the user agent which
the organization provides for its employees. Because the company controls
the user agents that will view its internal content - the author has very
accurate knowledge of the technologies that those user agents
support.

(Note that in example 4, the author is not specifying the user agent:
the company had specified the user agent in advance. The author just has
knowledge that only that agent is used so the author has very good
knowledge of the technologies the user agent supports. Care must be taken
here however since that agent would have to be cross-disability accessible
or else the author's assumptions may be bad because users with disabilities
may have to use other user agents to access the content.)

Developers may use technologies that are not in the specified baseline
provided that the both of the following are true:

All content and functionality must be available using only the
technologies in the specified baseline

The non-baseline technologies must not interfere with (break or block
access to) the content

when used with user agents that only support the baseline
technologies,

when used with user agents that support both the baseline and the
additional technologies.

Some initial guidance in choosing a baseline

Choosing baseline
technologies is a decision based on what technologies you can assume are
supported by the user agents of your audience at the time the baseline is
defined. When making the baseline decision, consider the following
factors.

INTRANET

If you are in a closed environment (Intranet) where the user agents used
are controlled and the Assistive Technology needed to make that user agent
accessible are known, then you can set a baseline that is tuned to the
capabilities of that user agent. Some questions to ask about that user agent
(and AT combination).

How well does the user agent satisfy the requirements of UAAG for each
technology being considered? A source of this information will be the
UAAG conformance statement for the user agent. The UAAG working group
also lists draft information about some user agents on its Web site.

What technologies does the user agent support? For example, what
version of HTML, XHTML, CSS, PDF, Flash etctera? (This information should
be available from the user agent vendor.)

Which versions of assistive technology products work with the user
agent? And which technologies are supported by the assistive technology,
e.g., does it support JavaScript? (This information should be available
from the assistive technology vendor.)

NOTE: Care must be taken when making assumptions about which assistive
technologies will be used in a company.

INTERNET

Most Web content is designed to be posted on the World Wide Web. For this
content it is not possible to know what platform or user agent people will be
using. It may be any one of many user agents running on any one of a number
of operating systems (Windows, Mac, Unix? Windows XP, Windows 2000, Windows
ME, Windowns 98, Windows 95). Sometimes service packs can make a difference.
When dealing with the Internet, it is therefore important to think in terms
of technologies and not browsers.

Below are some question to consider.

For which platforms and operating systems is a user agent available for
each technology being considered? Windows, Mac, Unix? Windows XP, Windows
2000, Windows ME, Windows 98, Windows 95, etc. Do operating system
Service Packs affect the accessibility of the user agent?

Is each candidate technology supported by a user agent (if one exists)
in all the languages used by the audience? Is it available in the
language of the content?

Is each candidate technology supported by recent versions of a user
agent your audience is using? Users don't always upgrade to newer
versions of user agents, or may not do so immediately.

Is each candidate technology supported only by user agents that are
very expensive so that the cost is likely to be prohibitive for the
audience, making it effectively unavailable?

If support for a technology by a user agent depends upon optional
software such as a plug-in, how difficult is it for users to obtain the
plug in? Will they be prompted to install the software automatically if
they try to use it? Is the accessible version of the plug-in different
from the one that is usually downloaded or pointed to? Do you need to
provide a link to the accessible version of the plug-in as part of the
content?

Does the technology have an open standard or a public
specification?

An appropriate baseline for accessible Web content will make a
conservative choice to ensure that users will have accessible user agents for
rendering the Web content. However, this does not prohibit the use of other
technologies, as long as they are used in such a way that user agents that
support only the technologies in the baseline can still render the content
accessibly.

Glossary

In the context of this document, an assistive
technology is a user agent that:

relies on services (such as retrieving Web resources and parsing markup) provided by
one or more other "host" user agents. Assistive technologies
communicate data and messages with host user agents by using and
monitoring APIs.

provides services beyond those offered by the host user agents to
meet the requirements of users with disabilities. Additional
services include alternative renderings (e.g., as synthesized
speech or magnified content), alternative input methods (e.g.,
voice), additional navigation or orientation mechanisms, and
content transformations (e.g., to make tables more accessible).

A statement which can be determined to be true or false, either by
machine or people knowledgeable in the field. When the test is done by
humans it would have to have high "inter-rater reliability"; at least 8
of of 10 people knowledgeable about web technology and technology for
people with disabilities would agree about whether the statement is
true or false.

Any software that retrieves and renders Web content
for users. This may include Web browsers, media players, plug-ins, and other programs — including assistive
technologies — that help in retrieving and rendering Web
content.